Fusion "Torch" USVs
"Single stage fusion rockets will be able to achieve velocities of 30,000 kps and more. At even a fraction of this velocity, the solar system will be a very small place." - Marshall T. Savage, The Millenial Project
Fusion “torch” drives differ from the fusion-pulse (Daedalus) drive featured elsewhere on this site in that a fusion reactor is used to super heat reaction mass (water, liquid hydrogen, methane, etc.), producing very high exhaust velocities. Specific impulse for a fusion torch in GURPS: Transhuman Space is around 14,400 seconds for a “high thrust” drive and 36,000 seconds for a “high impulse” drive. Researchers at the University of Michigan have suggested that a specific impulse in excess of 100,000 seconds may be obtainable with future fusion rockets.
The following tabletop gaming model is intended to represent a fusion torch USV. Note that the drive is mounted at the end of a boom away from the propellant tanks to protect the vessel from the enormous heat generated by the fusion reactor. The design was inspired by some of the conceptual spacecraft drawings featured on the Transhuman Space “Concept Art” page and Win Barker’s site. Win did the wonderful profile view of a hypothetical fusion torch USV at the top of this page.